The present disclosure relates in general to the enhancement of a plasmonic structure's bandwidth to improve its overall performance. More specifically, the present disclosure relates to using the enhanced bandwidth plasmonic structure in a variety of optoelectronic applications, including analyzing chemical and biological samples.
Surface plasmons are produced from the interaction of optical energy with a conductive material at a metal-dielectric interface. Under specific conditions, the incident optical energy couples with the conductive material to create self-sustaining, propagating electromagnetic waves known as surface plasmons. Once launched, surface plasmons ripple along the metal-dielectric interface and do not generally stray from this narrow path.
Surface plasmon resonance (SPR) sensing is a powerful and quantitative system and methodology for identifying the interactions of a variety of chemical and biological processes. SPR sensing provides a means for not only identifying chemical and biological interactions and quantifying their kinetic and energetic properties, but also for performing very sensitive detection of chemical and biological substances. Contemporary SPR sensing may be accomplished using plasmons generated at a metal/dielectric interface, with the metal typically being gold. See, for example, J. Homola et al., “Surface Plasmon Resonance Sensors: Review,” Sensors and Actuators B: Chemical 54, 3 (1999).
For chemical/biological sensing/detecting applications, the plasmon resonance frequency must have sufficient overlap with the characteristic vibration frequency of the molecule of interest in order to achieve the necessary interaction between the plasmons and the molecule of interest. Thus, when used in SPR sensing, an important design goal for plasmonic structures is providing sufficient overlap between the plasmon resonance frequency and the vibration frequency of the molecule of interest. This overlap of the two frequencies is known generally as frequency matching. In practice, it can be difficult to fabricate a conducting material having plasmons at a specific resonance frequency because the factors that shift plasmon resonance frequency are numerous and relatively difficult to control.